This application is a continuation of international patent application no. PCT/EP00/05373, filed Jun. 10, 2000, designating the United States of America, the entire disclosure of which is hereby incorporated herein by reference. Priority is claimed based on Federal Republic of Germany patent application no. DE 199 30 614.1, filed Jul. 2, 1999.
The invention relates to a filter cartridge, in particular for the air filter of an internal combustion engine, in which the air filter has a housing for holding the filter cartridge with an inlet for untreated air and an outlet for clean air, in which the filter cartridge comprises a filter medium that preferably is folded in a zigzag shape (i.e., pleated) and is provided with sealing elements on end plates disposed at the axial end faces of the cartridge.
A filter cartridge of this type is known, for example, from published international patent application no. WO 95/19382. The filter cartridge is arranged in a housing that has an inlet for untreated air and an outlet for clean air. The filter cleans the intake air in an internal combustion engine. Since the filter cartridge is replaced at regular intervals, it must be manufactured as economically as possible. The filter cartridge must also be easy to remove and install, as well as assure a reliable seal between the region of untreated air and the region of clean air.
This known filter cartridge is clamped between two concentric surfaces of the filter housing. The clamping action also simultaneously creates a seal, which must be maintained during shock or vibration.
A disadvantage of this system is that each filter cartridge has certain linear tolerances. As a result, clamping the filter cartridge in the housing creates a clamping force that is greater or smaller, depending on the linear proportions. A clamping force that is too great causes deformation of the filter cartridge, whereas a clamping force that is too small creates sealing problems in the filter cartridge during vibration.
It is an object of the invention to provide an improved filter cartridge which avoids the aforementioned disadvantages.
Another object of the invention is to provide a filter cartridge which can compensate for dimensional tolerances.
A further object is to provide a filter cartridge which produces a reliable seal between an untreated air space and a clean or filtered air space.
These and other objects are achieved in accordance with the present invention by providing a filter cartridge for installation in an air filter having a housing for holding the filter cartridge with an inlet for untreated air and an outlet for filtered air; the filter cartridge comprising an annular filter medium, end plates on axial end faces of the annular filter medium, and seal elements on the end plates; wherein a support body is provided interiorly adjacent the filter medium, and the support body is provided with support surfaces for axial and radial positioning of the cartridge at the end of the filter cartridge that faces the clean air outlet of the housing when the cartridge is installed in the housing; and wherein the seal element on the end plate of the filter cartridge that faces the clean air outlet when the cartridge is installed in the housing extends along the support body and the support surfaces and rests against an annular support surface.
In accordance with a further aspect of the invention, the objects are achieved by providing a filter cartridge comprising a cylindrical air filter element comprised of an annular filter medium, a base plate, a deformable outlet end plate having an outlet for filtered air, and a support tube integrated into the filter cartridge, the support tube forming a friction-locked connection with the outlet end plate and having an elastic zone at the end of the support tube adjacent the friction-locked connection.
In yet another aspect of the invention, the objects are achieved by providing a filter assembly comprising a filter housing with an inlet for untreated air and an outlet for filtered air, and a substantially cylindrical filter cartridge arranged in the housing between the inlet and the outlet, wherein the filter cartridge is mounted on a connection piece at the filtered air outlet and has an internal support body provided with support surfaces adjacent the connection piece for axially and radially positioning the filter cartridge, and wherein a seal element is provided in the vicinity of the support surfaces for sealing the filter cartridge to the housing.
A significant advantage of the invention is that the function of mounting the filter cartridge in the housing is separated from the function of creating a reliable seal between the untreated air space and the clean air space. The filter cartridge is mounted or fixed by means of a support body having support surfaces, and a reliable seal is created between the untreated air space and the clean air space by a sealing element located in the vicinity of the support body. The support body is preferably a hollow cylindrical, perforated element made of an injection-molded synthetic resin material. Such an element can be manufactured with high precision, thus eliminating the need for tolerance compensation. Any linear tolerance of the filter cartridge, therefore, does not affect the sealing function of the sealing element.
According to one embodiment of the invention, the sealing element and the end plate of the filter cartridge are combined as a single part. Polyurethane foam is suited for this purpose on account of its high elasticity. A further advantage of using polyurethane foam is the ease of thermal disposal of the used filter cartridge by incineration.
In a further embodiment of the invention, the filter cartridge is directly or indirectly supported by the housing wall or by a lid, on the side opposite from the clean air connection piece. Additional support elements or means of attachment, therefore, are not necessary.
A further embodiment of the invention involves pre-separation of dust particles. An axial cyclone is arranged in the region of the untreated air inlet so as to impart a swirling flow to the inflowing untreated air, causing coarse contaminant particles to precipitate on the inner wall of the housing. The particles may be removed via a discharge valve, for example.
In another aspect, the invention relates to a filter housing for a substantially cylindrical filter cartridge, the filter housing having an inlet for untreated air and an outlet for clean air. The filter housing is provided with a connection piece in the region of the clean air outlet. A filter cartridge is affixed to the connection piece by means of an internal support body that has support surfaces in the region of the connection piece for axial and radial positioning.
In addition, a seal element is provided on the filter cartridge to create a reliable seal between the untreated air space and the clean air space.
In accordance with another advantageous embodiment, the filter cartridge may be provided with a sealing system that uses synthetic resin materials of varying hardness. Thus, the sealing bead can have a very low Shore hardness of 20 to 30, for example, and the end plate made of a hard synthetic resin material can have a Shore hardness of 40 to 60, for example. A stable filter cartridge as well as a good sealing action are thus assured.
In a further embodiment, instead of a seal in the support tube, a circumferential sealing bead is provided on the side opposite from the clean air opening. The sealing bead rests against the lid or cover and forms a reliable seal between the untreated air space and the clean air space.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.